We propose to purchase a Momentum magnetic particle imaging (MPI) scanner for the F.M. Kirby Research Center at the Kennedy Krieger Institute (KKI). There is currently only one commercial demonstrator MPI scanner on the West Coast and no such instrument is presently available at KKI, Johns Hopkins University or the entire East Coast. The MPI scanner is needed to address the needs of 11 animal researcher groups at the KKI and Johns Hopkins University, who presently have 14 NIH-funded projects with several aims that can strongly benefit from the unique technical capabilities provided by the MPI technology. The F.M. Kirby Center, which opened in 1999, provides state-of-the-art technology and unique MRI expertise to facilitate the biomedical MRI research of scientists at several institutions in Maryland and throughout the USA. Initially only for human research, in 2011 the Center underwent a large expansion with a pre-clinical animal imaging center to add molecular, cellular and functional imaging facilities to its central function as a resource for KKI and JHU. The overall mission of the center is to have basic research and human applications in a combined setting to promote efficient translation of the technology to the clinic. The animal imaging center makes available state-of-the-art horizontal bore 11.7T and vertical bore 17.6T high-resolution MRI scanners as well as an IVIS optical/micro-CT scanner. The MPI scanner is needed for realizing the full research potential of the research center. This proposed instrumentation will provide unique benefits for many users: Unlike MRI, MPI enables straightforward quantitation of the superparamagnetic iron oxide (SPIO) nanoparticles since in MPI SPIO is a tracer and not a contrast agent, being detected directly. This allows one to do dose-response studies, e.g. a) How many stem cells or immune cells are at the target site, and how do therapeutic outcomes correlate to these cell numbers? b) For gene and drug delivery in theranostic applications, how many nanoparticles need to accumulate at the target site to induce the desired (anti-tumor) response? c) What is the minimal SPIO dose that is locally required to induce effective hyperthermia? The SPIO-based MPI technique has a high sensitivity, unlike MRI it can be used in tissues with injury and hemorrhage, it can perform whole-body mouse imaging within a single short scan, and the images can be easily overlaid on anatomical MR or CT images, with both of these modalities being located next door in the F.M. Kirby Research Center.